Bicycle Gears: 6-speed, 7-speed, 8-speed, 9-, 10-, 11-, ...?

Component manufacturers like to sell you lots of new parts, even if you don't need them. This has led to much confusion as various parts are labeled as if they are incompatible with other parts even though they are actually usable with little or no problem. Also, design often is churned by spec hype, and "keeping up with the Joneses," as in more sprockets, lighter weight, higher-priced components must be better. "Jones" is also a slang term for a drug addiction!

In reality, the fancier parts aren't always the most suitable, in the same way that a Ferrari, while it is a great racecar, isn't at all as good for daily transportation as a Toyota -- there are practical issues of cost, reliability, serviceability and durability. With bicycle components, the performance gain with higher-end models is often minuscule. Remember, you account for 80 percent of the weight even if you are riding a rather heavy bicycle!

There are, on the other hand, some real compatibility issues.

The following parts only are "speed specific":

Indexed Shifters These need to have the spacing of detents ("clicks") to match the system they'll be used with. This usually goes along with the correct number of clicks -- though a shifter with an extra click also can work, as long as the spacing is OK. (Friction shifters have no compatibility issues, they work with everything.)

Cassettes It is really the cassette that determines how many speeds you have in back.

Campagnolo/Shimano 8-speed cassettes have different spacing , so you can't generally get good indexing using a Campagnolo 8-speed wheel with a Shimano shift system or vice versa.

With 7-, 9- and 10-speed systems, the sprocket spacing between brands is close enough that it rarely causes any difficulty in practice.

Chain As you go to more sprockets on the cassette, you need a narrower chain. However, using a chain one size narrower than standard rarely presents any problem. Thus, you can use a "9-speed" chain with a 7-speed or 8-speed system, or a "10-speed" chain with a 9-speed system. This is not the ideal approach -- shifting may not be quite as smooth -- but it's workable.

Narrow chains bring other problems, though. They are usually more expensive and -- with 10 or more speeds -- don't last as long -- even when used in the intended system.

The narrowest chains also are more trouble to maintain. A master link, the SRAM PowerLink, makes it easy to disconnect a chain for cleaning. The 7/8 speed SRAM PowerLink works with SRAM and Shimano chains, probably others too. The 9-speed PowerLink works reliably with SRAM chains, but it may lead to a Shimano chain's jumping forward. The 10-speed SRAM Powerlock (note different name) is good for one-time use only: You must install a new one every time you reconnect the chain -- but then, if the chain has worn significantly, it will cause a "clunk" every time it comes around, because this one link is shorter than the others! Wipperman makes a similar "Connex" link for 10-speed chains and it is re-usable; there is also one from KMC. Shimano's 9- and 10-speed system is more trouble: you must press in a special link pin, using a special tool, every time you reconnect the chain, and this, too will cause a "clunk.

But What About...?

Within a given brand/style of rear derailer, all "speed numbers" are generally interchangeable. This applies to all indexable models, basically everything manufactured since the late 1980s. There are a few exceptions:

Campagnolo's first attempt at indexed shifting, "Synchro" was designed to work with older Campagnolo derailers, but the cable travel was too short and cable tension too high for reliable indexing. In the early 1990s, Campagnolo abandoned the Synchro system and redesigned everything around a longer cable travel. I don't know the exact year of this change, but I believe it happened at the same time as the move from 7-speed to 8-speed.

Campagnolo made a very slight change in indexing in 2001. Supposedly, you need to use 2001 or later shifters with 2001 or later rear derailers, but the difference is so small that it doesn't matter in practice.

Shimano "Dyna-Sys" shifters and derailers use a longer cable pull than other Shimano models, and must be used together.

SRAM has two different derailer systems.

Most SRAM derailers are fully interchangeable with Shimano systems.

SRAM "ESP" or "Exact Actuation" derailers and shifters (generally designated by a decimal model number: 7.0, 8.0, 9.0 etc) can only be used if the shifter and rear derailer are both ESP. A Jtek ShiftMate pulley adaptor can make a SRAM shifter work with a Shimano derailer, or vice versa. All SRAM 10-speed derailers and shifters are of yet a third type.

Front derailers don't generally care how many gears you have in back, though models designated for higher numbers of speeds may have slightly narrower cages , so they might be a bit more fussy in adjustment/trim when used with wider chains.

"Triple" front derailers have a wide, shaped inner cage plate. They generally work OK with double chainrings as long as the step between the chainring sizes is matched to the derailer.

"Double" front derailers work well with triple chainrings as long as the step between the outer and middle chainrings is only 4 or 5 teeth (as in a half-step system). If the step is larger, shifting from the small to the middle chainring will require some care and skill. In fact, you may need to upshift all the way to the big chainring, then jump back down to the middle.

Wheels/Hubs

There's considerable interchangeability among hubs . If you're upgrading from a system with fewer than 8 rear sprockets to one with more, you may need to concern yourself with the frame spacing. See my Frame Spacing Article for details on this.

The freewheel threading on these older hubs is generally interchangeable except for some very old French units. If you go from a 5-speed freewheel to a 6- or 7-speed freewheel, you will usually need to add some spacers to the right end of the axle between the cone and the locknut. Once you have done this, you'll also need to re-dish the wheel to bring the rim back to the centerline. You may need to re-space the frame if you have added spacers to the axle. See my Frame Spacing Article for details on this.

Shimano 5-speed and 6-speed shifters are made to index with the 5.5 mm spacing between sprockets on older 5- speed and 6-speed freewheels (or even, some new freewheels made as replacements). Without indexing, and because chains with protruding rivets are no longer widely available, it is possible to shift partway between sprockets and for the chain to "skate" along one side of a sprocket and on top of the teeth of the next-smaller sprocket. On the other hand, old SunTour "Ultra" freewheels and modern 7-speed freewheels have 5 mm spacing and will index with Shimano or SRAM 7-speed shifters, or 8-speed shifters with alternate cable routing. On an older freewheel without Hyperglide (or similar) shaped sprocket teeth, shifting will not be as clean as on a modern freewheel or cassette, but the indexing will work.

Cassette sprocket-tooth widths

Up through 9-speeds, all cassettes use very nearly the same width of sprocket teeth, and will work with 7/8 or 9-speed chains. Old Uniglide 6-speed cassettes have larger spacing between sprockets, and like older freewheels, have the same shifting issues.

10-speed sprocket teeth are narrower, to cram in one more sprocket. As a result, 10 speed sprockets do not wear as long. The structural strength of 10 speed sprockets also can be a concern; some have bent, a problem unheard of with other cassettes. Manufacturers have come up with clever ways to strengthen a cassette by riveting several sprockets together or machining them out of one piece of metal, but generally at increased cost, and of having to replace several sprockets at a time when only one is worn.

Campagnolo Cassette Systems

Campagnolo 8-speed cassettes used a slightly different spline pattern from the current pattern used for 9-and 10-speed systems.

8-speed Campagnolo cassettes will not fit on newer "9-speed" and "10-speed" hubs.

9- and 10-speed Campagnolo cassettes will not fit on 8-speed hubs.

It is theoretically possible to upgrade Campagnolo 8-speed hubs with newer cassette bodies, but in practice the parts don't generally seem to be available.

Shimano Freehub Cassette Systems (and copies)

In general, all Shimano Cassette Freehubs will work with all Shimano cassettes, any number of speeds. There are a very few exceptions:

Chainrings/Cranks

Old Chainrings, New Chains

There is a lot of confusion about the compatibility of narrow 9- and 10-speed chains with older cranksets. Shimano says you should replace the inner chainring(s) with specially designated 9- or 10-speed ones, but then they're all too eager to sell you stuff, whether you need it or not.

These chainrings have the teeth slightly farther to the right than the older chainrings to work a little better with the narrower chains. There is no difference whatever in the crank spiders.

The manufacturers also are concerned about clueless users. The worst-case scenario is that you will be riding along with the bike in its highest gear (large front, small rear) and then for some bizarre reason shift down in front before downshifting in the back. (There is no shift pattern in which it is reasonable to shift in this sequence.) [Not with a 9- or 10-speed cassette, to be sure -- John Allen] If you do shift this way, there's a small chance that the chain might "skate" over the edges of the teeth for maybe half a turn.

In practice this "problem" almost never materializes. Many, many cyclists are using 9- and 10-speed chains with older cranksets and having no problems whatever.

New Chainrings, Old Chains

Going the other direction, using wider chains with chainrings intended for narrower chains is not generally a major problem if there's only a one- or two- generation difference. The only problem you might run into is that the chain will be more liable to rub on the inside of the bigger chainrings in the small/small crossover gears, gears you shouldn't be using in any case.

"Road" vs. "Mountain" Cassettes, Derailers and Hubs

When discussing cassettes, the terms "Road" and "Mountain" are marketing terms, not technical ones.

"Road" vs. "Mountain" Cassettes

Cassettes come in various gear ranges, and the ones where the sizes are close together, with no really large sprockets, are commonly referred to in marketing-speak as "road" cassettes. Wide-range cassettes, with larger sprockets, are commonly called "mountain" or "MTB" cassettes.

"Road" vs. "Mountain" Rear Derailers

Similarly, derailers come in long-, medium- and short-cage versions. Shimano designates them: SGS (long), GS (medium), and SS (short.) The short cage ("road") ones only work with narrow range ("road") cassettes, because they don't have enough capacity to take up chain slack for use with a wide-range cassette. Short- and medium- cage derailers are also limited in terms of the largest rear sprocket that they can clear without having the jockey pulley rub on the sprocket. Generally, SS & GS rear derailers won't work properly with rear sprockets larger than 30 teeth.

Long-cage (SGS) derailers have greater takeup capacity, and work with all types of cassettes. Long-cage derailers are commonly called "mountain" derailers currently, though in the past, this style of derailer was known as a "touring" derailer. (The marketeers retired the use of "touring" as a buzzword in the late '80s when mountain bikes became the hot item.)

"Road" vs "Mountain" Front Derailers

While rear indexing is the same for all recent shifters/derailers, Shimano fronts use a different amount of cable pull for drop-bar vs flat-bar controls.

An additional complication is that "road" front derailer cages are shaped to fit well with a 52-53 tooth big chainring, while most current "mountain" front cages are shaped to fit with a 42-44 tooth big ring.

This makes it difficult if you want to use a "road" crankset, with full-sized chainrings (52, 53 top) with straight handlebars, or if you want to use a "mountain" crankset (42-48 tooth top) with drop-bar STI shifters.

"Road" vs. "Mountain" Hubs

"Road" and "Mountain" cassettes and hubs are interchangeable as long as the number of sprockets matches.

Although "Road" and "Mountain" hubs are no different as far as cassette fitting is concerned, they are different in terms of overall spacing. "Road" hubs generally use 130 mm spacing, while "mountain" hubs are 135 mm.

"Mountain" hubs will likely be slightly better sealed against dirt and mud than "road" hubs, but this is rarely an issue in practice. The wider 135 mm spacing will generally result in a slightly stronger wheel due to reduced dishing of the spokes.